refactor(decompress): move no-progress threshold policy to Rust

ZSTD_NO_FORWARD_PROGRESS_MAX is a compile-time override that was returned
directly by the C adapter. Keep the active build value in C, where
configuration belongs, but pass it through an ABI-checked scalar projection to
Rust. Rust now owns the policy boundary and preserves the exact configured
threshold, while the existing stalled-stream comparison, error mapping, and
private DCtx layout remain unchanged.

Test Plan:
- `git diff --cached --check` -- passed
- Cargo, make, builds, native tests, and heavy verification were not run per
  request.

lib/decompress/zstd_decompress.c

@@ -187,6 +187,15 @@ typedef char ZSTD_rust_decompress_stack_callbacks_layout[
 size_t ZSTD_rust_decompress_stack_action(
         const ZSTD_rustDecompressStackProjection* projection,
         const ZSTD_rustDecompressStackCallbacks* callbacks);
+typedef struct {
+    int configured_max;
+} ZSTD_rustNoForwardProgressProjection;
+typedef char ZSTD_rust_no_forward_progress_projection_layout[
+        (offsetof(ZSTD_rustNoForwardProgressProjection, configured_max) == 0
+         && sizeof(ZSTD_rustNoForwardProgressProjection) == sizeof(int))
+        ? 1 : -1];
+int ZSTD_rust_no_forward_progress_policy(
+        const ZSTD_rustNoForwardProgressProjection* projection);
 typedef struct {
     unsigned configured_level;
 } ZSTD_rustLegacySupportProjection;
@@ -316,7 +325,10 @@ size_t ZSTD_rust_dctx_default_max_window_size(void)
 
 int ZSTD_rust_no_forward_progress_max(void)
 {
-    return ZSTD_NO_FORWARD_PROGRESS_MAX;
+    ZSTD_rustNoForwardProgressProjection const projection = {
+        ZSTD_NO_FORWARD_PROGRESS_MAX
+    };
+    return ZSTD_rust_no_forward_progress_policy(&projection);
 }
 
 int ZSTD_rust_heapmode(void)